B-site mixed cationic tetrahedral layer confined the concentration and mobility of interstitial oxygen in mellite family

Li, Xiaohui; Wei, Xianyi; Wang, Xiaoge; Lou, Chenjie; Zhang, Wenda; Xu, Jungu; Luo, Zhaoji; Tang, Mingxue; Deng, Sihao; He, Lunhua; Xing, Xianran; Sun, Junliang; Kuang, Xiaojun

doi:10.1039/d2ta08334e

Cited by 5 publications

(7 citation statements)

References 61 publications

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“…[10] The second-order quadrupolar broadening combined with a distribution of chemical shifts typical of disordered systems results in broad 71 Ga NMR resonances, especially at 9.4 T, as also observed in previous 71 Ga MAS NMR experiments on LaSrGa 3 O 7 at 23.5 T under ν r of 30 kHz [11] and related melilite phases. [12][13][14] Striking resolution enhancement is observed as B 0 is increased up to 35.2 T owing to the inverse proportionality of the second-order quadrupolar broadening to B 0 in Hz and B 0 2 in ppm, thus enabling the identification of several resonances which are unresolved at lower B 0 . In particular, the remarkable spectral resolution achieved at 35.2 T allows the unambiguous detection of two 71 Ga resonances in the 71 Ga Quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) [15,16] spectrum of LaSrGa 3 O 7 .…”

Section: Resultsmentioning

confidence: 99%

Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy

Corti,

Hung,

Venkatesh

et al. 2024

ChemPhysChem

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Multinuclear Nuclear Magnetic Resonance (NMR) spectroscopy of quadrupolar nuclei at ultrahigh magnetic field provides compelling insight into the short‐range structure in a family of fast oxide ion electrolytes with La1+xSr1–xGa3O7+0.5x melilite structure. The striking resolution enhancement in the solid‐state 71Ga NMR spectra measured with the world’s unique series connected hybrid magnet operating at 35.2 T distinctly resolves Ga sites in four‐ and five‐fold coordination environments. Detection of five‐coordinate Ga centers in the site‐disordered La1.54Sr0.46Ga3O7.27 melilite is critical given that the GaO5 unit accommodates interstitial oxide ions and provides excellent transport properties. This work highlights the importance of ultrahigh magnetic fields for the detection of otherwise broad spectral features in systems containing quadrupolar nuclei and the potential of ensemble‐based computational approaches for the interpretation of NMR data acquired for site‐disordered materials.

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Section: Resultsmentioning

confidence: 99%

Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy

Corti,

Hung,

Venkatesh

et al. 2024

ChemPhysChem

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“…Inspired by the confinement of the concentration and mobility of interstitial oxygen by the B-site mixed cationic tetrahedra layer in the melilite family, it could be promising to design the pure Ga/Al composition at the B-, C-, and D-sites, such as La 3 (Ga/Al) 6 O 13.5 with the higher concentration of oxygen vacancy, in conjunction with aerodynamic levitation (ADL) coupled with the laser heating method. The ADL coupled with the laser heating method has the ability to break through the traditional solid solution limit to increase the concentration of oxygen defects, as evidenced in the melilite family La 1+ x AE 1– x (Ga/Al) 3 O 7+ x /2 (AE = alkaline earth) of La 2 Ga 3 O 7.5 and La 1.5 Ca 0.5 Al 3 O 7.25 .…”

Section: Resultsmentioning

confidence: 99%

“…Among these structures with an open structural framework, the classical structure type is a melilite structure. Melilite structure can be described as having a general formula of A 2 B(B′ 2 O 7 ) and adopts a two-dimensional layered network composed of corner-sharing tetrahedral anionic B(B′ 2 O 7 ) layers with 5-fold rings (Figures a and b), showing open structural frameworks with structural/compositional flexibility in accommodating interstitial oxygens. − Melilite La 1.54 Sr 0.46 Ga 3 O 7.27 shows excellent interstitial oxide ion conductivity of ∼0.02 S/cm at 600 °C, higher than the most commonly used electrolytes . The migration mechanism of interstitial oxide ions in melilite La 1.54 Sr 0.46 Ga 3 O 7.27 was through a cooperative mechanism involving the concerted knock-on motion of interstitial and lattice oxide ions .…”

Section: Introductionmentioning

confidence: 99%

The Langasite Family for the Development of Oxygen-Vacancy-Mediated Oxide Ion Conductors

Luo,

Li,

Wang

et al. 2024

Chem. Mater.

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Melilite-type oxide ion conductors have promising advantages in lowering the operating temperature of SOFCs due to the open structural framework with the deformation and rotation flexibility of the two-dimensional (2D) tetrahedral layers. Here, we have demonstrated the ability of a melilite-like langasite family (A 3 BC 3 D 2 O 14 ) with a three-dimensional (3D) open structural framework with more structural and compositional flexibility to a c c o m m o d a t e a n d t r a n s p o r t o x y g e n v a c a n c i e s i nLa 3 Ga 5+x Ge 1−x O 14−x/2 by Ga 3+ substitution for Ge 4+ . Unlike the high oxygen vacancy formation energies in the melilite structure, the existence of octahedral units makes oxygen vacancy formation in langasite more energy-favorable, and the oxygen vacancies favor the bridging O3 site between the octahedral and tetrahedral units. Instead of the transformation of octahedral and tetrahedral units into five-and three-coordinated units, respectively, the oxygen vacancies are stabilized by the local structural relaxation transforming both the Ga1O 6 and Ga3O 4 units around the O3 vacancy into five-coordinated GaO 5 units in the langasite La 3 Ga 5+x Ge 1−x O 14−x/2 , as evidenced by neutron diffraction data, atomistic static lattice simulations, the atomic pair distribution function, and reverse Monte Carlo simulations. Moreover, the combined molecular dynamics simulations and BVSE calculations give the 2D long-range transport of oxygen vacancy within the ab layer of langasite through the oxygen exchanges at all the crystallographic distinct O1, O2, and O3 sites and the continuous opening and reformation of the 6-fold rings assisted by the polyhedral rotation and deformation. The langasite La 3 Ga 5+x Ge 1−x O 14−x/2 with a 3D melilite structure exhibits superior thermo-mechanical stability compared to the 2D melilite structure, which is potentially advantageous for SOFC applications. This study provides the langasite structure as a new structure type for developing vacancy-mediated oxide ion conductors with structural flexibility.

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“…Indeed, the combined DFT and KMC simulations on La 1.5 Sr 0.5 Ga 3 O 7.25 by Schuett et al 44 also revealed that the interaction of interstitial defects with the local cation and anion environment plays a crucial role in determining the interstitial ion migration barrier and therefore the oxide ion conductivity. In addition, Li et al 120 recently explored the effect of mixed cations/valences in the tetrahedral layers over the stabilization and migration of O int . For that purpose, the authors prepared different nonstoichiometric Ca 2−x La x Ga 2 GeO 7+0.5x (0 ≤ x ≤ 0.15) compounds.…”

Section: Melilite-type Oxide Ion Conductorsmentioning

confidence: 99%

Oxide Ion-Conducting Materials Containing Tetrahedral Moieties: Structures and Conduction Mechanisms

2023

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This Review presents an overview from the perspective of tetrahedral chemistry on various oxide ion-conducting materials containing tetrahedral moieties which have received continuous growing attention as candidates for key components of various devices, including solid oxide fuel cells and oxygen sensors, due to the deformation and rotation flexibility of tetrahedral units facilitating oxide ion transport. Emphasis is placed on the structural and mechanistic features of various systems ranging from crystalline to amorphous materials, which include a variety of gallates, silicates, germanates, molybdates, tungstates, vanadates, aluminates, niobate, titanates, indium oxides, and the newly reported borates. They contain tetrahedral units in either isolated or linked manners forming different polyhedral dimensionality (0 to 3) with various defect properties and transport mechanisms. The development of oxide ion conductors containing tetrahedral moieties and the elucidation of the roles of tetrahedral units in oxide ion migration have demonstrated diverse opportunities for discovering superior electrolytes for solid oxide fuel cells and other related devices and provided useful clues for uncovering the key factors directing fast oxide ion conduction.

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B-site mixed cationic tetrahedral layer confined the concentration and mobility of interstitial oxygen in mellite family

Abstract: Melilite-type oxide ion conductors usually was observed in pure gallate compounds. Here a new mellite interstitial oxide ion conductor Ca2-xLaxGa2GeO7+x/2 (0  x  0.15) was developed by the substitution...

Cited by 5 publications

References 61 publications

Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy

Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy

The Langasite Family for the Development of Oxygen-Vacancy-Mediated Oxide Ion Conductors

Oxide Ion-Conducting Materials Containing Tetrahedral Moieties: Structures and Conduction Mechanisms

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B-site mixed cationic tetrahedral layer confined the concentration and mobility of interstitial oxygen in mellite family

Abstract: Melilite-type oxide ion conductors usually was observed in pure gallate compounds. Here a new mellite interstitial oxide ion conductor Ca2-xLaxGa2GeO7+x/2 (0  x  0.15) was developed by the substitution...

Cited by 5 publications

References 61 publications

Local Structure in Disordered Melilite Revealed by Ultrahigh Field 71Ga and 139La Solid‐State Nuclear Magnetic Resonance Spectroscopy

Local Structure in Disordered Melilite Revealed by Ultrahigh Field 71Ga and 139La Solid‐State Nuclear Magnetic Resonance Spectroscopy

The Langasite Family for the Development of Oxygen-Vacancy-Mediated Oxide Ion Conductors

Oxide Ion-Conducting Materials Containing Tetrahedral Moieties: Structures and Conduction Mechanisms

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Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy

Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid‐State Nuclear Magnetic Resonance Spectroscopy